Machine for manufacturing a coil of a pipe by bending it

ABSTRACT

The present invention relates to equipment for manufacturing heat exchange apparatus and more particularly to a machine for manufacturing a coil of a pipe by bending it by means of movable clamps. The invention ensures the manufacturing of a coil with bends whose radius as measured from the central axis of the pipe is within the range of from 0.8 to 1.5 of the outside diameter of the pipe, which is due to an improvement of the bending mechanism and its substantial simplification by dispensing with the master form. The coil is formed in a horizontal plane, with the position of the longitudinal axis of the pipe being bent remaining unchanged and without rotating the pipe about its axis.

omanov et a1.

tet [1 1 1451 Nov. 5, 1974 MACHINE FOR MANUFACTURKNG A COlllL OF A PIPEBY EENDHNG 117 [22] Filed: Jan. 19, 1973 [21] Appl. No.: 325,196

[52] US. C1. 72/310, 72/316, 72/318,

72/342, 72/D1G. 16, 140/71 R [51] Int. Cl. 321d 111/07- [58] Field ofSearch 72/144, 217, 218, 342,

72/296-298, 308-310, 316, 318, DIG. l2, DIG. 16, 307; 29/157.3 R;113/118 R;

[5 6] References Cited UNlTED STATES PATENTS 2,316,049 4/1943 Connor..72/217 2,345,102 3/1944 Dick 2,453,868 11/1948 Shaw,.|r. 2,454,29011/1948 Payne ..72/144 5 3 "M1,; 7 50 L i 47 45 2,535,328 12/1950Somerville 72/217 2,565,940 8/1951 Armstrong et a1 72/D1G. 16 2,582,5761/1952 Zweyer 72/183 X 3,406,551 10/1968 Coody 72/166 3,407,850 10/1968Kelm 72/702 X 3,742,749 7/1973 Bondarenko 72/217 FOREIGN PATENTS ORAPPLICATIONS 2,057,227 1971' France 72/342 630,232 10/1949 Great Britain72/342 7 Primary Examiner-Charles W. Lanham Assistant ExaminerD. M.Gurley Attorney, Agent, or Firm--Waters, Roditi, Schwartz & Nissen [5 7]ABSTRACT The present invention relates to equipment for manufacturingheat exchange apparatus and more particularly to a machine formanufacturing a coil of a pipe by bending it by means of movable clamps.The invention ensures the manufacturing of a coil with bends whoseradius as measured from the central axis of the pipe is within the rangeof from 0.8 to 1.5 of the outside diameter of the pipe, which is due toan improvement of the bending mechanism and its substantialsimplification by dispensing with the master form. The coil is formed ina horizontal plane, with the position of the longitudinal axis of thepipe being bent remaining unchanged and without rotating the pipe aboutits axis.'

13 Claims, 12 Drawing Figures O 5 .6. Q K .3 & 3 St S a a Q k V QR S TAMNR M N SE Q v m NW v fi m Jm /& H & m w f m Q J::::::.:. m S v w ill m//,/./14/a4r'a,'r4 %N WW. g Y Q wmkmba w M Q 7 w a Q PATENTEMuv 5 WPATENTEHNHV 51914 3.845550 Y SHEET ESP 8 PATENTEUNuv 51914 3845650 sawso? a PATENTEDIBV m 38456350 SHEEI 7 OF 8 FIG. I!

MACHINE FOR MANUFACTURHNG A COHL UP A PIPE BY BENDHNG IT The presentinvention relates to equipment for manu-,

facturing heat exchange apparatus and more particularly to a machine formanufacturing a coil of a pipe by bending it by means of movable clamps.

The invention may be the most advantageously used in manufacturingtubular heating surfaces of boilers. Furthermore, the. invention mayfind application in manufacturing heat exchange apparatus for thechemical and oil industry, as well as in the ship building.

The attempts to make a coil of a relatively long pip'e by bending thelatter in the cold state about a master form are widely known. Theseattempts are associated with the use of a slewing table mounted on thebase of a machine and supporting a master form and a clamp. Mounted onthe slewing table is also a clamping slider adapted to urge the pipeagainst said master form. Upon fixing the pipe in the clamp the slewingtable is rotated, and the pipe is bent about the master form whilesimultaneously being moved so as to follow the clamp. Due to frictionforces created between the pipe and the clamping slider the latter movesfollowing the pipe thus withstanding reaction forces arising duringthebending. After a bend has been formed the pipe is released from theclamp, moved in the axial direction up to a point of formation ofthenext bend and rotated at 180 about its longitudinal axis. Then thebending is effected in the same order and in the same direction asdescribed above. Asthe coil making proceeds, it besliders, as well asrelative movement of these devices are associated with the employment ofcomplicated mechanisms which considerably increase the cost of themachine and make its operation more difficult. Major difficulties arisein the case, where it is required to make coils of pipes havingdifferent diameter on the same machine. In such cases it is necessary toreplace the master form, both clamping sliders and the jaws of comesmore and more difficult to rotate the pipe at e 180 for making the nextbend.

This embodiment of the machine permits to dispense with the step ofrotating the coil at 180 after the formation of the next bend. it issufficient to release the clamp and the clamping slider, and to lowerthe master form and said clamp. Then the master form is shifted to theother side with respect to the longitudinal axis of the pipe, theposition of the pipe remaining unchanged, the master form and theclamping slider are lifted up to a level of the pipe and moved close tothe pipe. The formation of the next bend is effected by bending the pipein the direction opposite to that selected for the preceding bend.

During the movement of the coil in the horizontal plane the latter isbased on a support performing the rotations synchronously with thiscoil. Thus, the manufacturing of the coil is substantially simpler, butcertain difficulties restricted the filed of application of thismachine. First of all, this is associated with the fact that the bendsof relatively small curvature can be formed in the above-describedmachine only by means of a mandrel which cannot be used in manufacturinga coil.

At the same time, complicated movements of the master form together withthe clamps and the clamping the clamps.

It should be also noted that the bends having relatively snall bendingradius, which are obtainable on known machines, are characterized byelevated ovality of the cross section, whereby reliability anddurability of the coils are reduced.

It is the main object of the invention to provide a machine formanufacturing a coil of a pipe by bending it in which the bendingmechanism is substantially simplified and which is provided with devicessubstituting the master forms.

The above object is accomplished by that in a machine for manufacturinga coil of a pipe by bending it comprising a bending mechanism having aslewing table supporting a pair of clamps for a pipe and capable ofperforming-additional movement transversally relative to the axis of thepipe being bent according to the invention there is provided means foraxially moving the pipe towards the bending mechanism, the pair ofclamps being mounted in such a manner that a gap defined by a pair ofjaws in one clamp be coaxial with similar gap in the other clamp, andthere is also provided means for raising movable parts which carry thejaw in each of said clamps. Mounted between the clamps is heating meansfixed to stationary base, the tube being fed towards said meansafterleaving a guiding sleeve mounted adjacent said heating means. Inthis embodiment of the machine aportion of the pipe being bent andheated up to a degree, at which the plasticity of metal is substantiallyincreased, can be readily bent, the adjacent cold portions of the pipeperforming the functions of a mandrel, while the clampsand the guidingsleeve functioning as the'master form and the clamping sliders. Thearrangement of the clamps and heating means is such that upon formingone bend and prior to the formation of another one, it is possible toposition the next clamp, which is to be put in operation, behind heatingmeans in the direction of the axial movement of the pipe.

Means for axially moving the pipe is adapted to impart to the pipeduring the bending a speed which is higher than the speed of movement ofthe clamps of the bending mechanism. In this case axial compression ofthe pipe takes place, whereby the reduction of the thickness of the pipewall in the zone of the bend is eliminated. Bonds and straight portionsof the coil will be of equal strength.

According to a preferable embodiment of the invention it is advantageousthat means for axially moving the pipe comprise a slider with a clampmounted in straight guides made in the stationary base, two screwssymmetrically arranged with respect tothe clamp cooperating with theslider, said screws being connected to a motor via a gear train. In thiscase the forces applied to the screws are uniformly distributed therebyincreasing service life of the mechanism.

It is advantageous to mount the slewing table in a holding ring havingeyes for passing therethrough parallel rods fixed to the stationarybase. In this case said holding ring is preferably connected to anactuating cylinder adapted to move the holding ring along said rods. Theslewing table is of circular shape, whereby reaction forces appearingduring the bending are distributed over relatively large surface.

In order to ensure the adjustment of the machine for a required bendingradius, is advantageous to provide adjusting movable stops on thestationary base adjacent the ends of said rods for limiting the movementof the housing along the rods. I

In order to ensure the control of said adjusting movable stops it isadvantageous to fix the ends of said rods to the stationary base bymeans of bushings disposed in holes appropriately made in said base,while the end of each bushing which faces the housing should be providedwith a threaded portion co-operating with the adjusting movable stopwhich comprises a nut and have teeth along its peripheral surface, saidteeth being in meshing engagement with a gearconnected to a mechanicaltransmission.

Synchronous movement of the adjusting movable stops disposed adjacentone and the same rod can be accomplished in the case, where the bushingslocated adjacent the ends of said rod have oppositely directed threads.In this case the gears fixed on one and the same shaft are in meshingengagement with the adjusting movable stops co-operating with thesebushings.

In order to provide for uniform distribution of a load between theadjusting movable stops, it isadvantageous that the shafts carrying thegears be interconnected by means of a mechanical transmission adapted toimpart rotation to all the shafts synchronously.

During the change of position of the adjusting movable stops it isnecessary to adjust the position of the clamps on the slewing table inorder that the gap between the jaws in each clamp be coaxial with thepipe being bent in the starting position, when adjusting the machine fora new bending radius. For this purpose it is expedient to providestraight guides on the slewing table in which a slider should bemounted, said slider carrying said pair of clamps and being connected tomeans for moving said slider along said guides. In this case the guidesshould be arranged transversally relative to the gap between the clampjaws.

The most simple structure of the clamps of the bending mechanism isobtained in the case, where their jaws are brought together only in theuppermost position, while remaining spaced apart in any other position.In order to do this, it is desirable that said movable parts carryingthe jaws of each clamp in the bending mechanism comprise two double-armlevers joined by means of a common hinge loaded by springs which bearagainst said slider. In this case one identical ends of these leversshould support a pair of the jaws, the other identical ends of saidlevers should be interconnected by means of a common hinge connected toan actuating cylinder, while the upward movement of said firstmentionedhinge should be limited. The limitation of the upward movement of saidhinge results in that at some instant during the movement of the pistonrod of the actuating cylinder upwards after the hinge movement has beenstopped, the actuating cylinder spaces apart the lower ends of thedouble-arm levers, and the jaws are brought together, whereby the pipeis fixed-in the clamp. During the downward movement of the piston rod ofthe actuating cylinder the jaws are spaced apart and remain in this openposition until complete lowering.

In order to the most completely utilize the capacity of means foraxially moving the pipe, it is advantageous to connect the slewing tableto the motor for rotating it by means of a self-braking worm gear, theworm wheel crown of said gear being preferably mounted on the slewingtable. During the bending a required force will be created by means foraxially moving the pipe under conditions of the eccentric arrangement ofthe clamps with respect to the axis of rotation of the slewing table. Inthis case the power of the slewing table motor is consumed only forreleasing the worm gear from the braking conditions.

In order to ensure permanent connection between the self-braking wormgear and the motor during the movement of said holding ring along therods, it is advantageous to provide on the worm shaft of said gear aspur gear which is in meshing engagement with another spur gearconnected to the motor, the width of the gear corresponding to theamount of movement of the slewing table transversally relative to thepipe being bent.

The reduction of the thickness of the pipe walls in the zone thereofbeing bent during the formation of a bend can be eliminated, if themotor of means for axially moving the pipe and the motor performing therotation of the slewing table comprise electric motors, said motorsbeing coupled by means of an electric circuit to a regulator of theratio between the rotational speeds of these motors.

The coil can be the most conveniently supported during its manufacturingin the case, where the rods, along which the holding ring moves, arehorizontally arranged.

Substantial advantage of this invention consists in that the machineensures'the manufacturing of a coil with bends, whose radius as measuredfrom the central axis of the pipe is within the range of from 0.8 to 1.5of the outside diameter of the pipe, the reduction of the thickness ofthe pipe within the zone of the bent portion of the pipe not exceeding0-20 percent depending upon the ratio between the thickness of the pipewall and the outside diameter thereof. An amount of the thicknessreduction is predetermined based upon the requirement of elimination ofthe formation of undulations on the inner side of the wall of the bentportion.

A specific embodiment of the invention will now be described withreference to the accompanying drawings, in which:

FIG. 1 shows a diagrammatic plan view of the machine partially insection;

FIG. 2 is an enlarged cross sectional view taken along the line II-II inFIG. 1;

FIG. 3 is an enlarged cross sectional view taken along the line IIIIIIin FIG. 1;

FIGS. 4 to 9 show the positions of the slewing table with the clamps andthe holding ring during the manufacturing of a coil in a reduced scale;

FIG. 10 is an enlarged diagrammatic view of the clamp of the bendingmechanism during the holding of the pipe;

FIG. 11 shows an enlarged view of the clamp in the position in which itsjaws are spaced apart;

FIG. 12 shows an enlarged view of the clamp in the lowermost position.

The machine for manufacturing a coil of a pipe 1 (FIGS. 1 and 2)comprises a holding ring 2 with eyes 3 accommodating bronze sleeves 4.Round steel rods 5 extend through the eyes 3. The endsof the rods 5 arereceived in steel bushings 6 fixed by means of bolts (not shown) inholes appropriately made in a stationary base plate of the base. Theholding ring 2 is connected to a piston rod 8 of a pneumatic actuatingcylinder 9 attached to the base 7. The actuating cylinder 9 imparts tothe holding ring 2 a movement along the rods 5 supportingthis ring priorto the formation of each bend. In this case the rods 5 and the-pistonrod 8 of the actuating cylinder 9 are disposed tranversally relative tothe pipe 1. The holding ring 2 supports a slewing table 10, a bronzesleeve 11 beingpress fitted into the holding ring 2 in order to reducefriction between the tableand the holding ring.

The lower part of the slewing table is provided with a worm wheel crownl2 meshing with a worm 13 mounted in bearings 14 received in holes madein an appropriate manner in the holding ring 2. Fixed on one and thesame shaft with the worm 13 is a spur gear 15 which is in meshingengagement with a spur gear 16 mounted in bearings 17 fixed to the base7. The shaft of the gear 16 isconnected to an electric motor 18 via areduction gear 19 and a coupling 20. The meshing engagement of the worm13 with the worm wheel crown 12 is made so as to be self-braking. Theelectric motor 18 is adaptedto continuously effect release of theengagement at a required speed during the bending, whereby the slewingtable 10 which is subjected to an axial force applied to the pipe 1,will rotate at a speed directly proportional to the speed of release.The slew- 1 ing table 10 is provided with a groove 21 accommodating aslider 22 having lateral projections 23 received in guiding slots 24 ofthe lateral walls of the table 10 which define the groove 21. The groove21 is arranged radially relativeto the axis AA of rotation of theslewing table 10. The slider 22 is connected to a screw 25 which engagesa threaded portion of the walls of a hole 26 provided in a projection 27of the slewing table 10. The screw 25 is rotated by means of handwheel28 during the adjustment of the machine for a desired bend radius of acoil. The slider 22 is provided with two recesses 29 accommodatingclamps 30 with the jaws. The jaws are so arranged in the clamps 30 thata gap defined by the jaws in one clamp is coaxial with similar gap inthe other clamp. Each clamp 30 is provided with means 31 comprising apneumatic cylinder which is adapted to raise and lower the pair of jawswhile bringing them together and apart respectively. p

' The slewing table 10, the clamps 30 and the holding ring 2 are themain assemblies of a bending mechanism 32. The pipe 1 is fed towards thebending mechanism 32 by means 33 (FIGS. 1 and 3).for axially moving thispipe, that is for moving the pipe 1 along the longitudinal axis BBthereof. Means 33 for axially moving the pipe comprise a slider 34mounted by means of guiding projections 35 in guiding slots 36 made in alateral part 37 of the base 7. In order to reduce friction during themovement of the slider 34 along the guiding slots 36 the latteraccommodate bronze inserts 38. The intermediate part of the slider isprovided with a recess 39 accommodating a clamp 40 with the jaws toreceive the pipe 1. The clamp 40 is controlled by means 41 comprising apneumatic cylinder. The upper part of the slider 34 is provided with tworecesses 42 symmetrical with respect to the clamp 40 accommodatingrectangular nuts 43. The nuts 43 co-operate with screws 44 mounted inbearings 45 disposed in holes appropriately made in the base 7 and inits lateral part 37. The screws 44 are connected to spur gears 46 whichare in meshing engagement with a spur gear 47. The spur gear 47 isadapted to impart rotation to the screws 44 from an electric motor 48connected to this spur gear via a coupling 49 and a reduction gear 50.

During the movement of the pipe 1 the position of its longitudinal axisBB in space remains unchanged. The pipe 1 is supported by a guidingsleeve 51 (FIGS. 1 and 2) rigidly secured to the base 7 by means of abracket 52. Mounted behind the guiding sleeve 51 in the direction ofmovement of the pipe 1 is an electric inductor 53 connected to anelectric transformer 54 by means of electric bars 55 (only one bar isshown). The longitudinal axis of the inductor is aligned with thelongitudinal axis BB of the pipe 1. The transformer 54 is fixed to thebase 7.

The bend radius is set prior to the manufacturing of a coil by changingthe position of adjusting movable stops 56 (FIG. 1) which comprise nutsand have straight teeth on the peripheral surface. The stops 56 areprovided with threaded holes by means of which each of these stopsco-operates with threaded portions made at the ends of the bushings 6extending inside the base 7, said bushings receiving said ends of therods 5. The teeth of the stops 56 co-operate with the teeth of spurgears 57 mounted on shafts 58. These shafts 58 are mounted in bearings59 received in holes appropriately made in the walls of the base 7. Theboth shafts 58 rotate synchronously due .to their interconnection bymeans of a shaft 60 mounted in bearings 61 transversally relative to theshafts 58 and bevel gears mounted on said shafts 58 and 60. Rotation isimparted to the shafts by means of a hand-wheel 63 fixed to one of theshafts 58. i

The direction of the thread in the stops 56 is selected so thatdepending upon the sense of rotation of the handwheel 63 these'stopscould be brought together or apart in each pair of them. The distancebetween these stops determines the amount of eccentricity e, that is thedistance between the axis AA of the slewing table 10 and thelongitudinal axis BB of the pipe 1. The bend radius of a coil accuratelycorresponds to the amount of eccentricity.

In the starting position of the bending mechanism the holding ring 2(FIG. 4) is retracted and bears against the stops 56. In this positionthe clamps 30 are arranged along the axis BB, and in the left hand oneof these clamps the jaws are spaced apart and lowered below the pipe.The jaws of the right hand clamp are raised and clamp the pipe (FIG. 2).Then the inductor 53 is energized together with means 33 for axiallymoving the pipe (FIGS. 1 and 3), and the worm gear is released byrotating the worm13. Under the action of a force applied to the pipe inthe direction of an arrow C the slewing table 10 begins to rotate due tothe presence of the arm creating torque. The portion of the pipe, inwhich a bend is formed, gradually passes through the inductor 53, isbeing'heated and simultaneously bent, the slewing table 10 at the sametime rotating in the direction of an arrow V. The portion of the pipe tobe bent which is heated to a degree at which metal plasticity ismaterially increased, can be readily bent, the adjacent cold portions ofthe pipe 1 performing the functions similar to the functions of amandrel in known machines, whereas the clamp 30 and the sleeve 51perform the functions of the master form of the clamp and of theclamping sliders.

Upon rotation of the slewing table 10 through 180 (FIG. a coil bend isformed. The inductor 53 is deenergized, the pipe 1 is released from theclamp 30 (FIG. 6) holding it during the rotation of the table 10, andthe pipe is moved in the direction of an arrow C under the action of anaxial force applied to the pipe 1 until the next portion of this pipe tobe bent is brought close to the inductor 53. At the same time theholding ring 2 is shifted in the direction of an arrow D (FIG. 6) bymeans of an actuating cylinder 9 (FIG. 1) until it bears against thestops 56 (FIG. 7). Then the pipe 1 is gripped by the clamp 30 disposedon the left side from the inductor 53, the inductor 53 is energized,means 33 for axially moving the pipe is energized, and the pipe beginsto be bent under the action of a force applied along the arrow C as aresult of rotation of the slewing table in the direction of an arrow W.The second bend of a coil is thus formed (FIG. 8). The inductor 53 isagain deenergized, the pipe is released from the clamp, and means foraxially moving the pipe moves the latter in the direction indicated bythe arrow C (FIG. 9) until the next portion of the pipe to be bent isbrought close to the inductor 53. Then the actuating cylinder 9 isenergized (FIG. 1), and the holding ring 2 is retracted in the directionindicated by an arrow M (FIG. 8). Subsequently the clamp, the inductor,the bending mechanism and means for axially moving the pipe operate inthe above-described order.

An important role is performed in the operation of the bending mechanism33 (FIGS. 1 and 2) by the clamps 30 which ensure the formation of thecoil bends on both sides from the longitudinal axis of the pipe. Themovable parts of each of these clamps comprise two double-arm levers 64(FIGS. 10, 11 and 12) having jaws a at the upper ends thereof. Theselevers have a common hinge mounted on a cross bar 66. This cross bar isrigidly secured to the upper ends of bolts 67 passed through holes 68 oftheslider 22. The lower end of each of the bolts 67 is provided with anut 69 and a locking nut 70.

The nuts 69 limit the upward movement of the cross bar 66 under theaction of compressed springs 71 disposed between the cross bar 66 andthe horizontal portion of the slider 22. The lower ends of saiddouble-arm levers are connected with links 72 by means of hinges 73.Said links 72 have a common hinge 74 by means of which these links areconnected to a piston rod 75 of a pneumatic cylinder of means 31.

With the cylinder of means 31 being deenergized, the cross bar 66 movesupwards under the action of the compressed springs 71 until the nuts 69bear against the horizontal portion of the slider 22. Then the cylinderof means 31 is actuated, and the piston rod 75 of this cylinder movesupwards in the direction indicated by an arrow E (FIG. 10), the lowerends of the doublearm levers are spaced apart, and the pipe 1 is clampedbetween the jaws a of these levers. This position corresponds to theposition taken by the assemblies of the machine shown in FIGS. 1, 2, 3and 4.

Upon the formation of the first bend (FIG. 5) of a coil, the piston rod75 of the pneumatic cylinder of means 31 moves downwards as indicated byan arrow K (FIG. 11), the lower ends of the double-arm levers 64 arebrought together, and the pipe 1 is released from the clamp 30. Duringfurther downward movement of the rod (FIG. 12) the cross bar 66 is alsoinvolved in the movement. The resistance of the springs 71 is overcome,and the jaws a of the clamp 30 are lowered together with the double-armlevers 64, whereby the rotation of the pipe during the formation of thenext bend will not be prevented. The position of the parts of the clamp30 shown in FIG. 12 corresponds to the position of the assemblies of themachine shown in FIG. 6.

The clamp 40 of FIGS. 1 and 3 of means 33 for axially moving the pipe 1differs from the clamp 30 of the bending mechanism only in that theformer do not have a cross bar and bolts connected to that cross bar, aswell as there are no springs. During the periodical movement of theslider 34 the clamp 40 holds the pipe 1 only during the movement of saidslider towards the bending mechanism 32.

If there is no correspondance between the speeds of means 33 for axiallymoving the pipe (FIG. 1) and of the motor 18 performing the rotation ofthe slewing table 10, the pipe walls thickness may be reduced within theportion being bent.

In order to eliminate this possibility, the electric motor 48 of saidmeans 33 and the electric motor 18 are coupled to a regulator of theratio between the rotational speeds of these motors by means of anelectric circuit 77. The regulator 76 is supplied from an AC network 78.

The above-mentioned ratio between the speeds is selected in such amanner that a speed exceeding the circumferential speed of movement ofthe clamp 30 of the bending mechanism 32 be imparted to means 33 foraxially moving the pipe during the bending. Accordingly, an axialcompression of the pipe 1 is created thereby eliminating the reductionof the wall thickness of this pipe 1 within the zone of the bend. Thebent and straight portions of the coil are of equal strength.

Reaction forces appearing during the axial compression ofthe pipe 1 areuniformly distributed between the screws 44 of means 33 for axiallymoving the pipe due to symmetrical arrangement of these screws withrespect to the line of application of this force, whereby service lifeof said means is increased.

The slewing table 10 is of circular shape, whereby the reaction forcesappearing during the bending are distributed over relatively largesurface.

The machine is readily adjustable for this or another bending radius bychanging the position of the stops 56. If a pipe of a diameter differentfrom that for which the machine has been adjusted is to be fed into themachine, it is sufficient to replace the guiding sleeve 51, the electricinductor 53 and the jaws a of the clamps 30 and 40.

What is claimed is:

1. ,A machine for manufacturing a coiled pipe by bending the latter,comprising: a turntable rotating alternately clockwise and anticlockwiseunder the action of said pipe and adapted to effect additional movementat right angles to the longitudinal axis of said pipe; means forimparting said additional movement to sai turntable in two mutuallyopposite directions; at least two clamps having jaws being provided onsaid turntable and mounted so that a gap formed by a pair of jaws in onesaid clamp is in coaxial alignment with a similar gap of the other clampwhile the machine is inoperative, said clamps being adapted toalternately engage said pipe after each rotation of said turntable;means in each of said clamps for raising and lowering movable partsthereof carrying the jaws; means for braking the rotational speed ofsaid turntable, said last-mentioned means together with said turntable,said means for moving the turntable at right angles to the longitudinalaxis of the pipe, and said clamps, forming a bending mechanism; heatingmeans mounted on a stationary base between said clamps and adapted toheat said pipe in the zones of formation of the U-bends of the coil; aguiding sleeve mounted on said stationary base adjacent said heatingmeans and adapted to facilitate passage there-through of said pipetoward said heating means while concurrently absorbing reaction forcesproduced by the bending of said pipe; means for moving said pipe alongits longitudinal axis toward said bending mechanism and interacting withsaid means for braking the rotations of said turntable in response tothe action of said means for axially moving said pipe, the latter meansimparting motion to said turntable through the medium of said pipe dueto the latter being fixed in one of said clamps; said pipe being bent inresponse to successively fixing said pipe in one of said clamps on saidturntable, heating said pipe in the zone of formation of the futureU-bend, moving said pipe along its longitudinal axis by said means forits axial movement and braking said turntable by said braking means asthis table rotates under-the action of said means fol-moving said pipealong its longitudinal axis, said turntable being rotated through themedium of this pipe and the braking of the table being necessary inorder to build up the required axial compression of said pipe so as toprevent or reduce the thinning of its walls in the zone of formation ofsaid U-bend; after completin g the formationof this U-bend and releasingsaid pipe from said clamp, shifting said turntable at right angles tothe longitudinal axis of said pipe and then advancing the latter towardsaid bending mechanism and fixing it in the other clamp, whereupon allsaid operations are resumed in the above-described succession.

2. A machine according to claim 1, wherein said means for axially movingsaid pipe comprise a slider having a clamp and mounted in straightguides made in said stationary base, said slider co-operating with twoscrews which are symmetrically arranged with respect to said clamp, saidscrews being connected to a motor by means of a gear train.

3. A machine according to claim 1, wherein said slewing table is mountedin a holding ring having eyes through which parallel rods extend, saidrods being fixed to said stationary base, and said holding ring beingconnected to an actuating cylinder adapted to move the ring along saidrods.

4. A machine according to claim 3, wherein adjusting movable stops areprovided adjacent the ends of said rods on said stationary base whichare adapted to limit the movement of said holding ring along said rods.

A machine according to claim 4, wherein the ends of said rods are fixedto said stationary base by means of bushings received in holesappropriately made in said base, the end of each bushing which facessaid holding ring being provided with a threaded portion cooperatingwith the adjusting movable stop which comprises a nut having teeth onthe peripheral surface thereof, said teeth being in meshing engagementwith a gear connected to a mechanical transmission.

6. A machine according to claim 5, wherein said bushings disposedadjacent the opposite ends of one and the same rod of said rods haveoppositely directed threads, said adjusting movable stops co-operatingwith said bushings being in meshing engagement with gears mounted on oneand the same shaft.

7. A machine according to claim 6, wherein said shafts carrying saidgears are interconnected by means 9. A machine according to claim 8,wherein said movable parts carrying said jaws of each of said clamps insaid bending mechanism comprise two double-arm levers joined by a commonhinge which is loaded by springs which bear against said slider, saidlevers carrying a pair of said jaws at one identical ends thereof,

while the other identical ends of these levers being interconnected bymeans of links having a common hinge which is connected to an actuatingcylinder, the upward movement of said first-mentioned common hinge beinglimited.

10. A machine according to claim 1, wherein said slewing table isconnected to a motor for rotating it by means of a self-braking wormgear, the crown of a worm wheel of said gear being mounted on saidslewing table.

11. A machine according to claim 10, wherein a shaft of the worm of saidself-braking worm gear is provided with a spur gear which is in meshingengagement with another spur gear connected to said motor, the width ofsaid spur gear corresponding to the amount of movement of said slewingtable transversally relative to the axis of said pipe being bent.

12. A machine according to claim 1, wherein a motor of said means foraxially moving the pipe and said motor performing the rotation of saidslewing table comprise electric motors and are electrically coupled bymeans of an electriccircuit to a regulator of the ratio between therotational speeds of these motors.

13. A machine according to claim 3, wherein said rods along which saidholding ring moves are horizontally arranged.

1. A machine for manufacturing a coiled pipe by bending the latter,comprising: a turntable rotating alternately clockwise and anticlockwiseunder the action of said pipe and adapted to effect additional movementat right angles to the longitudinal axis of said pipe; means forimparting said additional movement to sai turntable in two mutuallyopposite directions; at least two clamps having jaws being provided onsaid turntable and mounted so that a gap formed by a pair of jaws in onesaid clamp is in coaxial alignment with a similar gap of the other clampwhile the machine is inoperative, said clamps being adapted toalternately engage said pipe after each rotation of said turntable;means in each of said clamps for raising and lowering movable partsthereof carrying the jaws; means for braking the rotational speed ofsaid turntable, said last-mentioned means together with said turntable,said means for moving the turntable at right angles to the longitudinalaxis of the pipe, and said clamps, forming a bending mechanism; heatingmeans mounted on a stationary base between said clamps and adapted toheat said pipe in the zones of formation of the U-bends of the coil; aguiding sleeve mounted on said stationary base adjacent said heatingmeans and datepd to facilitate passage there-through of said pipe towardsaid heating means while concurrently absorbing reaction forces producedby the bending of said pipe; means for moving said pipe along itslongitudinal axis toward said bending mechanism and interacting withsaid means for braking the rotations of said turntable in response tothe action of said means for axially moving said pipe, the latter meansimparting motion to said turntable through the medium of said pipe dueto the latter being fixed in one of said clamps; said pipe being bent inresponse to successively fixing said pipe in one of said clamps on saidturntable, heating said pipe in the zone of formation of the futureU-bend, moving said pipe along its longitudinal axis by said means forits axial movement and braking said turntable by said braking means asthis table rotates under the action of said means for moving said pipealong its longitudinal axis, said turntable being rotated through themedium of this pipe and the braking of the table being necessary inorder to build up the required axial compression of said pipe so as toprevent or reduce the thinning of its walls in the zone of formation ofsaid U-bend; after completing the formation of this U-bend and releasingsaid pipe from said clamp, shifting said turntable at right angles tothe longitudinal axis of said pipe and then advancing the latter towardsaid bending mechanism and fixing it in the other clamp, whereupon allsaid operations are resumed in the above-described succession.
 2. Amachine according to claim 1, wherein said means for axially moving saidpipe comprise a slider having a clamp and mounted in straight guidesmade in said stationary base, said slider co-operating with two screwswhich are symmetrically arranged with respect to said clamp, said screwsbeing connected to a motoR by means of a gear train.
 3. A machineaccording to claim 1, wherein said slewing table is mounted in a holdingring having eyes through which parallel rods extend, said rods beingfixed to said stationary base, and said holding ring being connected toan actuating cylinder adapted to move the ring along said rods.
 4. Amachine according to claim 3, wherein adjusting movable stops areprovided adjacent the ends of said rods on said stationary base whichare adapted to limit the movement of said holding ring along said rods.5. A machine according to claim 4, wherein the ends of said rods arefixed to said stationary base by means of bushings received in holesappropriately made in said base, the end of each bushing which facessaid holding ring being provided with a threaded portion co-operatingwith the adjusting movable stop which comprises a nut having teeth onthe peripheral surface thereof, said teeth being in meshing engagementwith a gear connected to a mechanical transmission.
 6. A machineaccording to claim 5, wherein said bushings disposed adjacent theopposite ends of one and the same rod of said rods have oppositelydirected threads, said adjusting movable stops co-operating with saidbushings being in meshing engagement with gears mounted on one and thesame shaft.
 7. A machine according to claim 6, wherein said shaftscarrying said gears are interconnected by means of a mechanicaltransmission to impart rotation to all said shafts synchronously.
 8. Amachine according to claim 6, wherein said slewing table is providedwith straight guides in which there is mounted a slider carrying saidpair of clamps and connected to means for moving said slider along saidguides, said guides being arranged transversally relative to said gapbetween said jaws of said clamps.
 9. A machine according to claim 8,wherein said movable parts carrying said jaws of each of said clamps insaid bending mechanism comprise two double-arm levers joined by a commonhinge which is loaded by springs which bear against said slider, saidlevers carrying a pair of said jaws at one identical ends thereof, whilethe other identical ends of these levers being interconnected by meansof links having a common hinge which is connected to an actuatingcylinder, the upward movement of said first-mentioned common hinge beinglimited.
 10. A machine according to claim 1, wherein said slewing tableis connected to a motor for rotating it by means of a self-braking wormgear, the crown of a worm wheel of said gear being mounted on saidslewing table.
 11. A machine according to claim 10, wherein a shaft ofthe worm of said self-braking worm gear is provided with a spur gearwhich is in meshing engagement with another spur gear connected to saidmotor, the width of said spur gear corresponding to the amount ofmovement of said slewing table transversally relative to the axis ofsaid pipe being bent.
 12. A machine according to claim 1, wherein amotor of said means for axially moving the pipe and said motorperforming the rotation of said slewing table comprise electric motorsand are electrically coupled by means of an electric circuit to aregulator of the ratio between the rotational speeds of these motors.13. A machine according to claim 3, wherein said rods along which saidholding ring moves are horizontally arranged.